Nginx as reverse proxy for Jetty

I need some help configuring nginx as a proxy in front of Jetty (on
Debian).

Jetty is serving my Java web app correctly, because if I test it with
this lengthier alternate notation (which I also used before setting up
the nginx proxy), the Java web app login page appears and I can log in:

But navigating to 'http://testapp001.com' still gives the error message
"403 - Forbidden"

Navigating to 'http://myhost.com:8080/testapp001.com' correctly displays
the login page of the Java web app and lets me log in successfully - so
Jetty and the web app are working - I just can't get the nginx reverse
proxy configured properly.